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A stoned P-plater was caught in dash-cam footage driving at 200km/h moments before he ploughed into another car and left an innocent woman to die.

Kayden James Lawson, 22, drove along a motorway on the NSW Central Coast so fast a truck he sped past shook, according to the truck driver, the Daily Mail reports.

"F**k me, he made the truck rock when he went past," the truck driver can be heard saying in dash-cam footage tendered at the Gosford District Court.

The footage then shows the green Holden Commodore Lawson was driving speed along the breakdown lane. Lawson then crashed into another vehicle and sent the innocent woman's car over a guardrail and 10 metres down an embankment.

"He just killed someone I think," the truck driver could be heard saying to another truck driver further up the M1 on two-way radio.

The woman, Kristyn Rourke, suffered a permanent brain injury and a fractured neck. Her face was de-gloved, she lost her right ear, and she had a near "complete traumatic amputation" of her left arm, Daily Telegraph reported.

Rourke, then a 38-year-old senior property manager, was trapped in the wreckage of her Toyota Hilux for an hour in the November 2014 smash. She spent six months in hospital.

Lawson had tried to flee the scene on a skateboard, and stood about a kilometre up the road with his finger out to hitchhike.

The Toyota Hilux was shunted 10m off the side of a bridge on the M1 at Morisset. Photo / Twitter